Corn is commonly grown as a row crop with the plants seeded and growing in rows that are typically 15 to 40 inches apart. When harvesting corn as grain, the corn plants are left in the field until they are fully mature and the kernels are dry. During growth the corn cobs typically upward and lean outward from the stalk however when fully mature the connection between the cob and the stalk dries out and the cobs fall to a downward orientation hanging down from the stalk. The dry stalks are also often leaning quite significantly from their vertical growth orientation.
Corn is typically harvested by mounting a corn header on a conventional combine. Slots on the corn header are configured to correspond to the spacing of the rows of corn. As the header moves down the rows, the cobs are stripped off the stalks and directed into the combine mechanism where the kernels are removed from the cobs and the cobs are directed back onto the field surface from the rear end of the combine. The cost of such a corn header is typically $50,000-$75,000 or more.
For crops other than corn, such as wheat, canola, and the like a conventional cutting header is used. Such conventional cutting headers have a knife extending across the entire width of the header. The knife comprises a knife bar extending along the front lower edge of the header, with a plurality of triangular knife sections attached to the bar such that the apex of the triangle extends forward from the bar. The exposed side edges of the knife sections are sharpened. Guards are attached to the front lower edge of the header and serve to protect the knife sections from breakage when contacting stones and like obstructions. The guards comprise pointed guard fingers extending forward, and the knife moves back and forth along the edge of the header in a slot cut laterally through the guard fingers. In addition to protecting the knife, the guard fingers also enable the knife sections to cut the crop. As the knife section moves back and forth it pushes crop against the sides of those portions of the guard finger that are above and below the slot, shearing the crop stalks.
The conventional knife operates in a vertical range from its lowest position a few inches above the ground to a maximum position that can be several feet above the ground. To pick up short crop plants and plants that are lying on the ground crop lifters are attached to the header and provide an arm of various designs that rides along the ground ahead of the knife, and a lifting finger extending at a shallow angle from the front of the arm up and back over the knife. U.S. Pat. Nos. 700,029 and 791,022 to Gatermann disclose such a crop lifter that is pivotally attached to the header so as to be able to move up and down to follow the ground. U.S. Pat. No. 4,120,138 to Schumacher illustrates a crop lifter that is fixed to the header instead of pivoting, but is made of spring steel so that same may move up and down to follow the ground.
In conventional headers loss also occurs in straight cut harvesting of crops such as dry beans, peas, milo, canola, and sunflowers due to heads or pods shattering or falling below the cutter bar. Dry, fragile seed pods often shatter when contacted by the harvesting equipment before they are on the header, and the shattered pods spill their seeds to fall on the ground. Seeds fall from the shattered pods down through the knife to the ground. While this problem of shattering seed pods and heads is more severe in some crops than others, there is generally at least some shattering loss in any crop.
Seed pans have been developed that attach to the front edge of the header and extend forward of the knife. The pans are spaced to form slots between the pans. The crop plants pass along the slots and are cut by the knife at the rear end of the slots. Seeds falling from the plants are caught in the pans and work their way rearward and onto the knife. Such seed pans are disclosed for example in U.S. Pat. No. 2,575,120 to Peel and U.S. Pat. No. 6,032,445 to Heintzman. The top surfaces of the pans are flat, with raised side walls to keep the seeds on the pan. The pans are configured to slope downward from front to rear so that the seeds move down the sloping surface onto the header and into the harvester. These seed pans are configured so that the slots between the pans are spaced to match the row spacing of the crops being harvested, such as soybeans, sunflowers, and the like that are typically planted in relatively widely spaced rows. Thus a large part of the knife is covered and not used.
U.S. Pat. No. 5,105,610 to Britten discloses crop stalk guides for attachment to a harvest header to provide crop dividers for separating the stalks in adjacent rows from one another. The Britten guides do not appear to catch falling seeds, as the guides comprise plates with flat top surfaces which have no walls to prevent seeds from falling off, but rather are simply used to guide the crop stalks into the knife. A plate is mounted to tops of two adjacent guard fingers and then bends slightly upward so it extends substantially horizontally forward at the same vertical level as the fingers when the fingers are in their working orientation sloping somewhat downward. The plates are mounted to the guards such that all guard fingers are covered by a plate, and the ends of the slots lie between adjacent guard fingers. The plates guide the stalks to each side and along a slot between the plates to the knife. The slots are much narrower than the spacing between the guard fingers, so at the rear ends of the slots where the knife is located, the plates must be notched so that the outer edges of the guard fingers are exposed to the knife sections to allow the knife sections to shear the stalks against the guard fingers.
Using conventional cutting headers to harvest corn is problematic. The corn plants are typically quite tall, and when dried out as they are at harvest time, the stalks often lean forward and sideways to the combine's operating travel direction such that the stalks themselves, or at least some of the cobs thereon, are not cut and carried onto the header but fall to the ground, and are wasted. Thus farmers who would like to grow corn as part of a crop rotation with other crops are faced with the large expense of buying a corn header for their combines, and so often simply leave corn out of the crop rotation.